I am new here and wondered if anybody could help with the following problem?

I have a Peavey 112 studio pro which sounded great - especially clean channel with lots of reverb but then...

I built a silicon fuzzface (BC108) and was testing it out yesterday through the amp. I got sound - albiet a little quiet. There a couple of crackle and then suddenly nothing but a loud low hum - sounds like mains hum. This does not vary in volume or frequency with changes in the amp's controls but is constant and loud.

I am assuming I have knackered the power stage - does this assumption seem correct? If I have would the home made pedal being plugged in have contributed to this and if so how?

Thank you for your help in advance.